Field of the Invention
The present invention relates to an image sensor using a nanowire and a method of manufacturing the same.
Description of the Related Art
An image sensor is a semiconductor device for converting an optical image into an electrical signal, and may include, for example, a CCD (Charge Coupled Device) image sensor and a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor. A CCD image sensor is a device configured such that MOS (Metal-Oxide-Silicon) capacitors are positioned very close to each other and charge carriers are stored in the capacitors and transported, and a CMOS image sensor is a device, which employs a switching mode, configured such that MOS transistors, provided in the same number as the number of pixels, are constituted through CMOS technology, using a control circuit and a signal processing circuit, which serves as a peripheral circuit, and are used to sequentially detect outputs.
The CMOS image sensor is advantageous compared to the CCD image sensor, which is widely used as an existing image sensor, because the operating mode is simple, a variety of scanning methods are possible, and a signal processing circuit may be integrated into a single chip, thus enabling the reduction in size of products, decreasing manufacturing costs thanks to the compatible use of CMOS technology, and lowering power consumption.
With advancements in image sensor technology, the size of photodiodes is gradually decreased in order to realize an increase in the number of pixels without increasing the size of chips, and thus the area of light-receiving units is reduced, resulting in deteriorated image quality. A typical image sensor has a front illumination structure, in which photodiodes are formed under the surface of the substrate, logic circuits are formed on the substrate, and light is radiated onto the upper surface of the substrate. However, light loss is caused by the upper layers formed on the photodiodes, undesirably deteriorating the light response characteristics of the photodiodes. Also, the penetration depth of photons is increased, making it difficult to convert the injected light flux into photocharges.